Japan in the Ancient World 

Japanese archaeologists divide the earliest part of Japanese history into four periods: the Paleolithic (preceramic) period, the Jomon (cord-marked pottery) period, the Yayoi period, and the Kofun (burial mound) period. Underlying this chronology, however, are two basic problems: First, who are the Japanese, and where did they come from? Second, how do the Japanese or "proto-Japanese" relate to the Ainu, a group of people who have resided in Japan since about 7500 B.C.E. but differ racially, culturally, and linguistically from modern Japanese in significant ways? 

Paleolithic Japan (before 10,000 B.C.E.)

The Japanese islands have probably been occupied by humans for at least 30,000 years, if not longer. However, 10,000 years ago, Paleolithic Japan was a cooler place, and the sea level was 125 feet (38 meters) lower; therefore, some of the archaeological evidence of the earliest inhabitants is submerged. These hunters and gatherers, who had an extensive stone-tool inventory, most likely came to southern Japan through present-day Korea or to northern Japan from eastern Siberia, though there is abundant evidence of land connections to Asia at this time throughout the islands. It appears that the complete physical separation of the Japanese islands occurred only as recently as 18,000 to 12,000 years ago.

Jomon period (c. 10,000-c. 300 B.C.E.)

Starting about 13,000 years ago, when the Japanese climate began to warm, beautiful local pottery traditions—characterized by complex impressions made by twisted cords or sticks on the outside of pots before baking—abruptly appeared at various locales. Such ceramics eventually became commonplace throughout the islands. The Jomon people (named for this distinctive "cord-marked" ceramic style) were probably the direct descendants of the people of the previous Paleolithic traditions. They were very successful at hunting, fishing, and gathering, and because of the numerous rivers and rugged coastlines, they were largely sedentary. Shell mounds all over the islands indicate how extensively the ocean and rivers were exploited by Jomon people. The Jomon pottery eventually came to show distinctive regional styles, suggesting the existence of rather well-defined cultural groups and local folk traditions.

Yayoi (c. 300 B.C.E.-c. 300 C.E.)

About two thousand years ago, a distinct break occurred in the archaeological record. In Kyushu, the southernmost main island of Japan, bronze from the Korean peninsula and a newer style of earthenware pottery appeared, and iron smelting was developed. These changes characterize the Yayoi period, named after the district in modern Tokyo where certain artifacts were first discovered. The Yayoi period also saw the beginning of Japanese-style intensive irrigated wet-rice cultivation, which became the main means of subsistence for almost everyone on the islands. This agrarian rice-based economy—with basically the same kind of farming practices—would persist until Japan's westernization in the late nineteenth century.

However, controversy surrounds the origins of this culture. The Yayoi people may have come from overseas and replaced the earlier Jomon people (as evidenced by the presence of many new technologies from abroad). For many years, Japanese archaeologists have assumed this to be true, with the implication being that the Jomon people are the ancestors of modern Ainu, and modern Japanese are the descendants of those who migrated from the Asian mainland during the Yayoi and Kofun periods. However, a majority of archaeologists feel that the record probably indicates a gradual but direct continuity from Jomon people to early, but historically identifiable, Japanese, with any migration from the mainland blending in with the local cultures. In either case, by the end of the Yayoi period, certain institutional structures were in place—a division of labor, the accumulation of prestige and luxury goods by particular individuals, and the rise of complex political organizations—which created a more stratified society, allowing for the development of a full-fledged Japanese state in the Kofun period.

https://www.ebsco.com/research-starters/history/japan-ancient-world